This invention relates to the catalytic, oxidative dehydrogenation of isobutyraldehyde to form methacrolein, particularly, using promoted iron phosphorus oxide catalysts.
The dehydrogenation of isobutyraldehyde, a product of the commercial oxo process, to form methacrolein, a monomer in the production of plastics or an intermediate in the preparation of methacrylate monomers, is disclosed in the prior art. For example, U.S. Pat. No. 3,329,724 discloses the production of methacrolein from isobutyraldehyde in the presence of oxides of molybdenum or oxides of uranium. U.S. Pat. Nos. 3,878,249 and 3,917,712 disclose the production of methacrolein by oxidation of isobutyraldehyde in the presence of a silver salt.
The dehydrogenation of aldehydes generally is disclosed in U.S. Pat. Nos. 3,308,194; 3,308,199; 3,649,560 and 3,960,767. Dehydrogenation of aldehydes in the presence of at least two halogens and an inorganic catalyst which may comprise an alkali metal oxide or hydroxide or alkaline earth metal oxide or hydroxide and a metal compound such as iron phosphate, among others, is disclosed in U.S. Pat. No. 3,207,806.
U.S. Pat. No. 3,948,959 discloses the preparation of unsaturated acids by oxidation of the corresponding saturated acid using iron phosphorus oxide catalysts promoted with Li, Na, K, Rb, Cs, Mg, Ca, Sr and Ba. U.S. Pat. Nos. 3,634,494; 3,652,654; 3,855,279; 3,917,673 and and 4,029,695 disclose the preparation of unsaturated acids and esters from saturated acids and esters using iron phosphorus oxide catalysts containing bismuth and/or lead promoters, optionally with other promoter elements, including Mn, U, Pr, Ca, Sr, and Cr. These prior art catalysts characteristically have exhibited short life and thermal instability.
It is therefore an object of the present invention to provide a process for the production of methacrolein from isobutyraldehyde utilizing catalysts having improved activity, improved catalyst life and thermal stability.